My limited tube rolling included , Shuguang 6SN7, Black Treasure 181Z for the front.
Shuguang KT88, Treasure KT88, Svetlana 6550, and Shuguang KT88 Cryoed.
Black Treasures both KT88 and 6SN7 sounded warmer through the mids, Svetlana 6550's sounded cooler top to bottom but lacked the visceral wallop this amplifier is capable of .
Kevin Hayes voices his amplifiers impeccably , you can always make your Vac Phi 300.1 sound different but not necessarily better.
I settled on original Shuguang 6SN7's front and Shuguang KT88 cryoed fron Upscale Audio, highly recomended.
I hope this help you in some way, Regards.